Electronic equipment, control information transmission and reception methods having bidirectional communication using predetermined lines

ABSTRACT

A communication method for performing transmission of video data and audio data, communication of device control data, and local area network communication by using a single cable may include connecting a connectable device to a pair of differential transmission lines; performing the local area network communication through bidirectional communication via the pair of differential transmission lines; and notifying a connection state of an interface with the connectable device by using a DC bias potential of at least one of the differential transmission lines of the pair. The connection state may include a first notification from a first one of the pair of differential transmission lines whether the connectable device is connected to the single cable.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/312,353, filed on Nov. 24, 2009, which application is a nationalphase entry under 35 U.S.C. §371 of International Application No.PCT/JP2007/071649 filed Nov. 7, 2007, published on May 15, 2008 as WO2008/056707 A1, which claims priority from Japanese Patent ApplicationNo. JP 2006-301486 filed in the Japanese Patent Office on Nov. 7, 2006,Japanese Patent Application No. JP 2007-050426 filed in the JapanesePatent Office on Feb. 28, 2007, and Japanese Patent Application No. JP2007-201517 filed in the Japanese Patent Office on Aug. 2, 2007, all ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to electronic equipment, a controlinformation transmission method, and a control information receptionmethod that employ a communication interface, for example, the highdefinition multimedia interface (HDMI). More particularly, the inventionis concerned with electronic equipment that includes a communicationunit which performs bidirectional communication using predeterminedlines included in a transmission line, that uses the communication unitto transmit control information to another electronic equipment, andthat thus can quickly control the operating state of the anotherelectronic equipment. The invention is concerned with electronicequipment that includes a communication unit which performsbidirectional communication using predetermined lines included in atransmission line, that uses the communication unit to receive controlinformation from another electronic equipment, that controls theoperating state on the basis of the control information, and that thuspermits quickly control of the operating state from the anotherelectronic equipment side.

BACKGROUND ART

In recent years, the HDMI has prevailed as a communication interfaceunder which a digital video signal, that is, a non-compressed (baseband)video signal (hereinafter, referred to as image data), and a digitalaudio signal accompanying the video signal (hereinafter, referred to asaudio data) are transmitted from, for example, a digital versatile disc(DVD) recorder, a set-top box, or any another audiovisual (AV) source toa television receiver, a projector, or any another display (refer to,for example, a patent document 1).

Between pieces of equipment interconnected under the HDMI, control isimplemented under the consumer electronics control (CEC) standardstipulated in the HDMI. However, the CEC standard succeeds a datastructure and a transmission speed defined for equipment control througha SCART (syndicat des constructeurs d'appareils radiorecepteurs etteleviseurs) terminal in an analog mode. Therefore the transmissionspeed for control information is as low as approximately 400 bps, andthe data structure is defined to basically support transmission in unitsof 16 bytes. The transmission speed and data structure are thereforeunsuitable for control that requires a high-speed response ortransmission of control information whose length exceeds 16 bytes.

In a patent document 2, a proposal is made of a technology in which whena received partial transport stream (TS) is outputted from atransmission unit to another video equipment or device, messageinformation alone is separated and extracted, converted into a universalplug and play (UPnP) representation, and then outputted from thetransmission unit. In a patent document 3, a proposal is made ofequipment in which: data and control information are transferred betweena receiving device and a recording device; and the receiving device sideincludes a processing means which deals with recording control.

-   Patent document 1: JP-A-2006-319503-   Patent document 2: JP-A-2006-319573-   Patent document 3: JP-A-2003-209775

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The technology described in the patent document 2 is not concerned withcontrol between pieces of equipment. The technology described in thepatent document 3 is concerned with control between pieces of equipmentbut is not concerned with control between pieces of equipmentinterconnected under the HDMI.

An object of the invention is to permit quick control of the operatingstate of a source equipment side from sink equipment.

Means for Solving the Problem

The concept of the invention lies in electronic equipment that includesa signal receiving unit which receives a video signal sent from anotherelectronic equipment over a transmission line by means of differentialsignals on multiple channels.

The electronic equipment is characterized in that: the electronicequipment further includes a communication unit which performsbidirectional communication using predetermined lines included in thetransmission line; and the communication unit transmits controlinformation, which is used to control at least the operating state ofthe another electronic equipment side, to the another electronicequipment.

The electronic equipment of the invention includes the signal receivingunit that receives a video signal sent from another electronic equipmentover a transmission line by means of differential signals on multiplechannels, and is, for example, HDMI-conformable sink equipment orrepeater equipment. In the invention, the communication unit thatperforms bidirectional communication using the predetermined linesincluded in the transmission line is further included. The communicationunit is used to transmit control information to another electronicequipment. In this case, the control information can be quickly sent toanother electronic equipment, and the operating state of the anotherelectronic equipment side can be quickly controlled.

In the invention, for example, a broadcast receiving unit that acquiresa video signal on a predetermined channel on the basis of a televisionbroadcast signal, a display unit that displays a picture represented bythe video signal acquired by the broadcast receiving unit, and a useroperating unit which a user uses to instruct recording of the videosignal relevant to the picture displayed on the display unit may befurther included. The communication unit may transmit not onlyinformation on channel selection in the broadcast receiving unit butalso information on recording instruction made using the user operatingunit. In this case, the channel selected in the broadcast receiving unitexisting on the another electronic equipment side can be switched to achannel relevant to the picture displayed on the display unit. Whenuser's recording instruction is made, a recording unit on the anotherelectronic equipment side can immediately initiate recording of a videosignal relevant to the picture displayed on the display unit.

In the invention, for example, a broadcast receiving unit that acquiresa video signal and an audio signal on the basis of a televisionbroadcast signal, a display unit that displays a picture represented bythe video signal acquired by the broadcast receiving unit, a loudspeakerthat outputs sounds represented by the audio signal acquired by thebroadcast receiving unit, and a user operating unit which a user uses todesignate an external audio output mode in which the sounds representedby the audio signal acquired by the broadcast receiving unit areoutputted through the external loudspeaker may be further included. Thecommunication unit may feed the audio signal acquired by the broadcastreceiving unit to the another electronic equipment, and may transmit thedesignating information on the external output mode entered using theuser operating unit. In this case, the audio signal acquired by thebroadcast receiving unit can be sent to the another electronic equipmentside. The sounds represented by the audio signal acquired by thebroadcast receiving unit can be outputted through the externalloudspeaker according to the user's designation of the external audiooutput mode.

In the invention, for example, a remote control signal receiving unitthat receives a remote control signal (remote control code) sent from atransmitter of the remote control signal may be further included. Thecommunication unit may transmit the remote control signal received bythe remote control signal receiving unit to another electronicequipment. In this case, when a user remotely controls the anotherelectronic equipment side, the communication unit can send a remotecontrol signal deriving from the remote control to the anotherelectronic equipment side. The operating state of the another electronicequipment side can be quickly controlled.

The concept of the invention lies in electronic equipment that includesa signal transmitting unit which transmits a video signal to anotherelectronic equipment over a transmission line by means of differentialsignals on multiple channels, and that further includes:

a communication unit that performs bidirectional communication usingpredetermined lines included in the transmission line; and

a control unit that controls the operating state on the basis of controlinformation received by the communication unit.

The electronic equipment of the invention includes the signaltransmitting unit that transmits a video signal to another electronicequipment over a transmission line by means of differential signals onmultiple channels, and is, for example, HDMI-conformable sourceequipment or repeater equipment. In the invention, the communicationunit that performs bidirectional communication using predetermined linesincluded in the transmission line is included. The control unit controlsthe operating state on the basis of the control information received bythe communication unit. In this case, the control information can bequickly received from the another electronic equipment, and quickcontrol of the operating state from the another electronic equipmentside is permitted.

In the invention, for example, a broadcast receiving unit that acquiresa video signal on a predetermined channel on the basis of a televisionbroadcast signal, and a recording unit that records the video signalacquired by the broadcast receiving unit may be included. The controlunit may control a channel, which is selected by the broadcast receivingunit, on the basis of information on channel selection received by thecommunication unit, and may also control the recording unit on the basisof the information on recording instruction, which is received by thecommunication unit, so that the recording unit will initiate recordingof the video signal acquired by the broadcast receiving unit. In thiscase, the channel selected by the broadcast receiving unit can beswitched to the channel relevant to the picture displayed on the displayunit existing on the another electronic equipment side. When user'srecording instruction is made on the another electronic equipment side,the recording unit can immediately initiate recording of the videosignal representing the picture displayed on the display unit on theanother electronic equipment side.

In the invention, for example, an audio output unit that outputs anaudio signal received by the communication unit to the loudspeaker maybe further included. The control unit may control the audio output uniton the basis of the designating information on the external audio outputmode, which is received by the communication unit, so that muting in theaudio output unit will be changed from an on state to an off state. Inthis case, the audio signal acquired by the broadcast receiving unit onthe another electronic equipment side can be received. When the user'sdesignating information on the external audio output mode is fed fromthe another electronic equipment side, muting in the audio output unitis changed from the on state to the off state. Control can beimmediately implemented in order to attain a state in which soundsrepresented by the audio signal acquired by the broadcast receiving uniton the another electronic equipment side can be outputted through theexternal loudspeaker.

In the invention, for example, the control unit may control the actionsof the respective units on the basis of a remote control signal receivedby the communication unit. In this case, the remote control signal istransmitted from another electronic equipment side, and the actions ofthe respective units can be quickly controlled.

Advantage of the Invention

According to the invention, a communication unit that performsbidirectional communication using predetermined lines included in atransmission line is included. The communication unit is used totransmit control information to another electronic equipment. Theoperating state of the another electronic equipment can be quicklycontrolled. According to the invention, a communication unit thatperforms bidirectional communication using predetermined lines includedin a transmission line is included. The communication unit is used toreceive control information from another electronic equipment. Anoperating state is controlled based on the control information. Theoperating state can be quickly controlled from the another electronicequipment side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing as an embodiment an example of theconfiguration of a communication system employing the HDMI;

FIG. 2 is a block diagram showing an example of the configuration of atelevision receiver serving as sink equipment;

FIG. 3 is a diagram showing the construction of an IP packet to be usedto transmit a remote control code;

FIG. 4 is a block diagram showing an example of the configuration of anaudio amplifier serving as repeater equipment;

FIG. 5 is a block diagram showing an example of the configuration of aDVD recorder serving as source equipment;

FIG. 6 is a block diagram showing an example of arrangement of an HDMItransmitting unit (HDMI source) and an HDMI receiving unit (HDMI sink);

FIG. 7 is a diagram showing the structure of TMDS transmission data;

FIG. 8 is a diagram showing the pin assignment (type A) of an HDMIterminal;

FIG. 9 is a connection diagram showing an example of arrangement of ahigh-speed data line interface 103 of a television receiver 100 and ahigh-speed data line interface 203 a of an audio amplifier 200;

FIG. 10 is a diagram for explaining a “one-touch recording” sequence ofrecording a picture (image), which is seen on the television receiver100, with a DVD recorder 300;

FIG. 11 is a diagram showing as a comparative example a “one-touchrecording” sequence to be employed in a case where a high-speed dataline interface is not included;

FIG. 12 is a diagram for explaining a “theater mode” sequence ofswitching audio outputs between the television receiver 100 and audioamplifier 200;

FIG. 13 is a diagram showing as a comparative example a “theater mode”sequence to be employed in a case where a high-speed data line interfaceis not included;

FIG. 14 is a diagram for explaining a “remote control” sequence; and

FIG. 15 is a diagram showing as a comparative example a “remote control”sequence to be employed in a case where a high-speed data line interfaceis not included.

DESCRIPTION OF REFERENCE NUMERALS

10: communication system, 100: television receiver, 101: HDMI terminal,102: HDMI receiving unit, 103: high-speed data line interface, 200:audio amplifier, 201 a, 201 b: HDMI terminal, 202 a: HDMI transmittingunit, 202 b: HDMI receiving unit, 203 a, 203 b: high-speed data lineinterface, 300: DVD recorder, 301: HDMI terminal, 302: HDMI transmittingunit, 303: high-speed data line interface, 400: receiving antenna, 500:5.1-channel loudspeaker group, 610, 620: HDMI cable.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, an embodiment of the invention will bedescribed below. FIG. 1 shows an example of the configuration of acommunication system 10 as an embodiment. The communication system 10includes a television receiver 100 serving as sink equipment, an audioamplifier 200 serving as repeater equipment, and a DVD recorder 300serving as source equipment. To the television receiver 100 and DVDrecorder 300, a television broadcast receiving antenna 400 is connected.To the audio amplifier 200, a 5.1-channel loudspeaker group 500 isconnected.

The television receiver 100 and audio amplifier 200 are interconnectedover an HDMI cable 610. The television receiver 100 is provided with anHDMI terminal 101 to which an HDMI receiving unit (HDMIRX) 102 and ahigh-speed data line interface (I/F) 103 included in a communicationunit are connected. The audio amplifier 200 is provided with an HDMIterminal 201 a to which an HDMI transmitting unit (HDMITX) 202 a and ahigh-speed data line interface (I/F) 203 a included in a communicationunit are connected. One end of the HDMI cable 610 is coupled to the HDMIterminal 101 of the television receiver 100, and the other end of theHDMI cable 610 is coupled to the HDMI terminal 201 a of the audioamplifier 200.

The audio amplifier 200 and DVD recorder 300 are interconnected over aHDMI cable 620. The audio amplifier 200 is provided with an HDMIterminal 201 b to which an HDMI receiving unit (HDMIRX) 202 b and ahigh-speed data line interface (I/F) 203 b included in a communicationunit are connected. The DVD recorder 300 is provided with an HDMIterminal 301 to which an HDMI transmitting unit (HDMITX) 302 and ahigh-speed data line interface (I/F) 303 included in a communicationunit are connected. One end of the HDMI cable 620 is coupled to the HDMIterminal 201 b of the audio amplifier 200, and the other end of the HDMIcable 620 is coupled to the HDMI terminal 301 of the DVD recorder 300.

FIG. 2 shows an example of the configuration of the television receiver100. The television receiver 100 includes the HDMI terminal 101, theHDMI receiving unit 102, the high-speed data line interface 103, anantenna terminal 105, a digital tuner 106, a demultiplexer 107, a movingpicture expert group (MPEG) decoder 108, a video signal processingcircuit 109, a graphic production circuit 110, a panel drive circuit111, a display panel 112, an audio signal processing circuit 113, anaudio amplification circuit 114, a loudspeaker 115, a digitaltransmission content protection (DTCP) circuit 116, an internal bus 120,a central processing unit (CPU) 121, a flash read-only memory (ROM) 122,a dynamic random access memory (DRAM) 123, an Ethernet interface (I/F)124, a network terminal 125, a remote control receiving unit 126, and aremote control transmitter 127.

Noted is that “Ethernet” is a registered trademark. The digital tuner106 and demultiplexer 107 constitute a broadcast receiving unit. Theremote control receiving unit 126 and remote control transmitter 127constitute a user operating unit.

The antenna terminal 105 is a terminal that inputs a televisionbroadcast signal received by the receiving antenna 400. The digitaltuner 106 processes the television broadcast signal inputted to theantenna terminal 105, and outputs a predetermined transport streamassociated with a user-selected channel. The demultiplexer 107 extractsa partial transport steam (TS) (a TS packet of video data and a TSpacket of audio data) from the transport stream obtained by the digitaltuner 106.

The demultiplexer 107 fetches a program-specific information/serviceinformation (PSI/SI) from the transport stream obtained by the digitaltuner 106, and outputs the PSI/SI to the CPU 121. The transport streamobtained by the digital tuner 106 has multiple channels multiplexedtherein. The processing in which the demultiplexer 107 extracts thepartial TS on an arbitrary channel from the transport stream is enabledby obtaining information concerning a packet ID (PID) on the arbitrarychannel from the PSI/SI (PAT/PMT).

The MPEG decoder 108 performs decoding processing on a video packetizedelementary stream (PES) packet formed with a TS packet of video dataobtained by the demultiplexer 107 so as to provide video data. The MPEGdecoder 108 performs decoding processing on an audio PES packet formedwith a TS packet of audio data obtained by the demultiplexer 107 so asto provide audio data. The MPEG decoder 108 performs decoding processingon the PES packets of a picture and sounds respectively, which aredecrypted by the DTCP circuit 116, so as to provide video data and audiodata.

The video signal processing circuit 109 and graphic production circuit110 perform, if necessary, multi-screen processing, graphic datasuperposing processing, or the like on video data obtained by the MPEGdecoder 108. The panel drive circuit 111 drives the display panel 112 onthe basis of the video data outputted from the graphic productioncircuit 110. The display panel 112 is formed with, for example, a liquidcrystal display (LCD), a plasma display panel (PDP), or the like. Theaudio signal processing circuit 113 performs required processing such asD/A conversion on the audio data obtained by the MPEG decoder 108. Theaudio amplification circuit 114 amplifies an audio signal outputted fromthe audio signal processing circuit 113, and feeds the resultant signalto the loudspeaker 115.

The DTCP circuit 116 encrypts, if necessary, a partial TS extracted bythe demultiplexer 107. The DTCP circuit 116 decrypts encrypted data fedfrom the network terminal 125 or high-speed data line interface 103 tothe Ethernet interface 124.

The CPU 121 controls the actions of the components of the televisionreceiver 100. The flash ROM 122 stores control software and preservesdata. The DRAM 123 forms a work area for the CPU 121. The CPU 121develops software or data, which is read from the flash ROM 122, in theDRAM 123, activates the software, and controls the components of thetelevision receiver 100. The remote control receiving unit 126 receivesa remote control signal (remote control code) transmitted from theremote control transmitter 127, and feeds the signal to the CPU 121. TheCPU 121, flash ROM 122, DRAM 123, and Ethernet interface 124 areinterconnected over the internal bus 120.

The HDMI receiving unit (HDMI sink) 102 receives video (image) data andaudio data of the baseband fed to the HDMI terminal 101 over the HDMIcable 610 through the communication in accordance with the HDMI. TheHDMI receiving unit 102 will be detailed later. The high-speed data lineinterface 103 is a bidirectional communication interface employingpredetermined lines (in this embodiment, a reserved line and an HPDline) included in the HDMI cable 610. The high-speed data line interface103 will be detailed later.

The actions in the television receiver 100 shown in FIG. 2 will bebriefly described below.

A television broadcast signal inputted to the antenna terminal 105 isfed to the digital tuner 106. The digital tuner 106 processes thetelevision broadcast signal, and outputs a predetermined transportstream associated with a user-selected channel. The predeterminedtransport stream is fed to the demultiplexer 107. The demultiplexer 107extracts a partial TS (a TS packet of video data and a TS packet ofaudio data) associated with the user-selected channel from the transportstream. The partial TS is fed to the MPEG decoder 108.

The MPEG decoder 108 performs decoding processing on a video PES packetformed with the TS packet of video data, and provides the video data.The video data is subjected to, if necessary, multi-screen processing,graphic data superposing processing, or the like by the video signalprocessing circuit 109 and graphic production circuit 110. Thereafter,the resultant video data is fed to the panel drive circuit 111. An imageassociated with the user-selected channel is displayed on the displaypanel 112.

The MPEG decoder 108 performs decoding processing on an audio PES packetformed with the TS packet of audio data, and provides the audio data.The audio data is subjected to required processing such as D/Aconversion by the audio signal processing circuit 113. After amplifiedby the audio amplification circuit 114, the resultant audio data is fedto the loudspeaker 115. Sounds associated with the user-selected channelare outputted through the loudspeaker 115.

When the television broadcast signal is received, a partial TS extractedby the demultiplexer 107 is encrypted by the DTCP circuit 116, and fedas transmitted data to the high-speed data line interface 103 via theEthernet interface 124. Therefore, the partial TS is transmitted to theaudio amplifier 200 over the predetermined lines of the HDMI cable 610coupled to the HDMI terminal 101.

When the television broadcast signal is received, if the partial TSextracted by the demultiplexer 107 is transmitted over a network, afterthe partial TS is encrypted by the DTCP circuit 116, the resultantpartial TS is outputted to the network terminal 125 via the Ethernetinterface 124.

The remote control receiving unit 126 receives a remote control code(remote control signal) sent from the remote control transmitter 127.The remote control code is fed to the CPU 121. If the remote controlcode relates to control of the television receiver 100, the CPU 121controls the components of the television receiver 100 on the basis ofthe remote control code.

The CPU 121 produces an IP packet containing the remote control code fedfrom the remote control receiving unit 126. The IP packet is outputtedto the HDMI terminal 101 via the Ethernet interface 124 and high-speeddata line interface 103. The IP packet is transmitted to the audioamplifier 200 side over the HDMI cable 610 coupled to the HDMI terminal101. The IP packet is, if necessary, transmitted over a network. In thiscase, the IP packet is outputted to the network terminal 125 via theEthernet interface 124.

FIG. 3 shows the construction of an IP packet containing a remotecontrol code. The IP packet is composed of an IP header, a payload, anda CRC. In the IP packet containing the remote control code, the remotecontrol code is inserted into the payload division.

After an encrypted partial TS that is fed from the network terminal 125to the Ethernet interface 124 or fed from the HDMI terminal 101 to theEthernet interface 124 via the high-speed data line interface 103 isdecrypted by the DTCP circuit 116, the decrypted partial TS is fed tothe MPEG decoder 108. Thereafter, the same actions as those performedwhen a television broadcast signal is received are carried out. An imageis displayed on the display panel 112, and sounds are outputted throughthe loudspeaker 115.

The HDMI receiving unit 102 acquires video (image) data and audio datathat are transmitted from the audio amplifier 200 side connected to theHDMI terminal 101 over the HDMI cable 610. The video data and audio dataare fed to the video signal processing circuit 109 and audio signalprocessing circuit 113 respectively. Thereafter, the same actions asthose performed when a television broadcast signal is received arecarried out. An image is displayed on the display panel 112, and soundsare outputted through the loudspeaker 115.

FIG. 4 shows an example of the configuration of the audio amplifier 200.The audio amplifier 200 includes the HDMI terminals 201 a and 201 b, theHDMI transmitting unit 202 a, the HDMI receiving unit 202 b, thehigh-speed data line interfaces 203 a and 203 b, an MPEG decoder 204, avideo/graphic processing circuit 205, an audio processing circuit 207,an audio amplification circuit 208, audio output terminals 209 a to 209e, a DTCP circuit 210, an Ethernet interface 211, an internal bus 212, aCPU 213, a flash ROM 214, and a DRAM 215.

The HDMI transmitting unit (HDMI source) 202 a transmits video (image)data and audio data of the baseband from the HDMI terminal 201 a overthe HDMI cable 610 through communication conformable to the HDMI. TheHDMI receiving unit (HDMI sink) 202 b receives video (image) data andaudio data of the baseband fed to the HDMI terminal 201 b over the HDMIcable 620 through communication conformable to the HDMI. The HDMItransmitting unit 202 a and HDMI receiving unit 202 b will be detailedlater.

The high-speed data line interface 203 a is a bidirectionalcommunication interface using predetermined lines (in the presentembodiment, a reserved line and an HPD line) included in the HDMI cable610. The high-speed data line interface 203 b is a bidirectionalcommunication interface using predetermined lines (in the presentembodiment, a reserved line and an HPD line) included in the HDMI cable620. The high-speed data line interfaces 203 a and 203 b will bedetailed later.

The DTCP circuit 210 decrypts an encrypted partial TS that is fed to theEthernet interface 211 via the high-speed data line interface 203 b. TheMPEG decoder 204 performs decoding processing on an audio PES packet outof the partial TS decrypted by the DTCP circuit 210, and thus providesaudio data.

The audio processing circuit 207 performs required processing such asD/A conversion on the audio data obtained by the MPEG decoder 204. Theaudio amplification circuit 208 amplifies a front left audio signal SFL,a front right audio signal SFR, a front center audio signal SFC, a rearleft audio signal SRL, and a rear right audio signal SRR, and outputsthe resultant signals to the audio output terminals 209 a, 209 b, 209 c,209 d, and 209 e respectively.

A front left loudspeaker 500 a, a front right loudspeaker 500 b, a frontcenter loudspeaker 500 c, a rear left loudspeaker 500 d, and a rearright loudspeaker 500 e constituting the loudspeaker group 500 areconnected to the audio output terminals 209 a, 209 b, 209 c, 209 d, and209 e respectively.

The audio processing circuit 207 performs required processing on theaudio data obtained by the HDMI receiving unit 202 b, and then feeds theresultant audio data to the HDMI transmitting unit 202 a. Thevideo/graphic processing circuit 205 performs processing such as graphicdata superposition on the video (image) data obtained by the HDMIreceiving unit 202 b, and then feeds the resultant data to the HDMItransmitting unit 202 a.

The CPU 213 controls the actions of the components of the audioamplifier 200. The flash ROM 204 stores control software and preservesdata. The DRAM 215 forms a work area for the CPU 213. The CPU 213develops software and data, which are read from the flash ROM 214, inthe DRAM 215, activates the software, and controls the components of theaudio amplifier 200. The CPU 213, flash ROM 214, DRAM 215, and Ethernetinterface 211 are interconnected over the internal bus 212.

The actions in the audio amplifier 200 shown in FIG. 4 will be brieflydescribed below.

In the HDMI receiving unit 202 b, video (image) data and audio data sentfrom the DVD recorder 300 connected to the HDMI terminal 201 b over theHDMI cable 620 are acquired. The video data and audio data are fed tothe HDMI transmitting unit 202 a via the video/graphic processingcircuit 205 and audio processing circuit 207 respectively, andtransmitted to the television receiver 100 over the HDMI cable 610coupled to the HDMI terminal 201 a.

In the high-speed line interface 203 a, an encrypted partial TStransmitted from the television receiver 100 over predetermined lines ofthe HDMI cable 610 coupled to the HDMI terminal 201 a is received. Thepartial TS is fed to the DTCP circuit 210 via the Ethernet interface211, and decrypted thereby.

The partial TS decrypted by the DTCP circuit 210 is fed to the MPEGdecoder 204. In the MPEG decoder 204, decoding processing is performedon a PES packet of audio data included in the partial TS in order toprovide the audio data. The audio data is fed to the audio processingcircuit 207 and subjected to required processing such as D/A conversion.When muting is set to an off state, various audio signals SFL, SFR, SFC,SRL, and SRR outputted from the audio processing circuit 207 areamplified and outputted to the audio output terminals 209 a, 209 b, 209c, 209 d, and 209 e respectively. Sounds are outputted through theloudspeaker group 500.

In the high-speed data line interface 203 a, an IP packet containing aremote control code and being transmitted from the television receiver100 over predetermined lines of the HDMI cable 610 coupled to the HDMIterminal 201 a is received. The IP packet is fed to the CPU 213 via theEthernet interface 211. When the remote control code contained in the IPpacket relates to control of the audio amplifier 200, the CPU 213controls the components of the audio amplifier 200 on the basis of theremote control code. For example, when the remote control coderepresents a designation of a “theater mode” as an external audio outputmode, the CPU 213 controls muting of the audio amplification circuit 208so that the muting will be changed from the on state to an off state.

The partial TS and IP packet received as mentioned above by thehigh-speed data line interface 203 a and fed to the Ethernet interface211 are fed as transmitted data to the high-speed data line interface203 b. The partial TS and IP packet are transmitted to the DVD recorder300 over predetermined lines of the HDMI cable 620 coupled to the HDMIterminal 201 b.

FIG. 5 shows an example of the configuration of the DVD recorder 300.The DVD recorder 300 includes the HDMI terminal 301, the HDMItransmitting unit 302, the high-speed data line interface 303, anantenna terminal 304, a digital tuner 305, a demultiplexer 306, aninternal bus 307, a recording unit interface 308, a DVD/BD drive 309, ahard disk drive (HDD) 310, a CPU 311, a flash ROM 312, a DRAM 313, anEthernet interface 314, a network terminal 315, a DTCP circuit 316, anMPEG decoder 317, a graphic production circuit 318, a video outputterminal 319, and an audio output terminal 320. The digital tuner 305and demultiplexer 306 constitute a broadcast receiving unit.

The HDMI transmitting unit (HDMI source) 302 transmits video (image)data and audio data of the baseband from the HDMI terminal 301 over theHDMI cable 620 through communication conformable to the HDMI. The HDMItransmitting unit 302 will be detailed later.

The high-speed data line interface 303 is a bidirectional communicationinterface using predetermined lines (in the present embodiment, areserved line and an HPD line) included in the HDMI cable 620. Thehigh-speed data line interface 303 will be detailed later.

The antenna terminal 304 is a terminal that inputs a televisionbroadcast signal received by the receiving antenna 400. The digitaltuner 305 processes the television broadcast signal inputted to theantenna terminal 304 and outputs a predetermined transport stream. Thedemultiplexer 306 extracts a partial transport stream (TS) (a TS packetof video data and a TS packet of audio data), which is associated with apredetermined selected channel, from the transport stream obtained bythe digital tuner 305.

The demultiplexer 306 fetches program-specific information/serviceinformation (PSI/SI) from the transport stream obtained by the digitaltuner 305, and outputs the PSI/SI to the CPU 311. In the transportstream obtained by the digital tuner 305, multiple channels aremultiplexed. The processing in which the demultiplexer 306 extracts thepartial TS on an arbitrary channel from the transport stream is enabledby acquiring information concerning a packet ID (PID) on the arbitrarychannel from the PSI/SI (PAT/PMT).

The CPU 311, flash ROM 312, DRAM 313, demultiplexer 306, Ethernetinterface 314, and recording unit interface 308 are interconnected overthe internal bus 307. The DVD/BD drive 309 and HDD 310 are connectedonto the internal bus 307 via the recording unit interface 308. TheDVD/BD drive 309 and HDD 310 record the partial TS extracted by thedemultiplexer 306. The DVD/BD drive 309 and HDD 310 reproduce thepartial TS recorded in a recording medium.

The MPEG decoder 317 performs decoding processing on a video PES packet,which is included in the partial TS extracted by the demultiplexer 306or reproduced by the DVD/BD drive 309 and HDD 310, and provides videodata. The MPEG decoder 317 performs decoding processing on an audio PESpacket included in the partial TS, and provides audio data.

The graphic production circuit 318 performs, if necessary, graphic datasuperposing processing or the like on the video data obtained by theMPEG decoder 317. The video output terminal 319 outputs the video datathat is outputted from the graphic production circuit 318. The audiooutput terminal 320 outputs the video data obtained by the MPEG decoder317.

The DTCP circuit 316 encrypts, if necessary, the partial TS extracted bythe demultiplexer 306 or the partial TS reproduced by the DVD/BD drive309 and HDD 310. The DTCP circuit 316 decrypts the encrypted data fedfrom the network terminal 315 or high-speed data line interface 303 tothe Ethernet interface 314.

The CPU 311 controls the actions of the components of the DVD recorder300. The flash ROM 312 stores control software and preserves data. TheDRAM 313 forms a work area for the CPU 311. The CPU 311 developssoftware and data, which are read from the flash ROM 312, in the DRAM313, activates the software, and controls the components of the DVDrecorder 300.

The actions in the DVD recorder 300 shown in FIG. 5 will be brieflydescribed below.

A television broadcast signal inputted to the antenna terminal 304 isfed to the digital tuner 305. In the digital tuner 305, a predeterminedtransport stream is fetched by processing the television broadcastsignal, and the predetermined transport stream is fed to thedemultiplexer 306. In the demultiplexer 306, a partial TS (a TS packetof video data and a TS packet of audio data) associated with apredetermined channel is extracted from the transport stream. Thepartial TS is fed to the DVD/BD drive 309 or HDD 310 via the recordingunit interface 308, and recorded based on a recording instruction sentfrom the CPU 311.

The partial TS extracted by the demultiplexer 306 or the partial TSreproduced by the DVD/BD drive 309 or HDD 310 is fed to the MPEG decoder317. In the MPEG decoder 317, decoding processing is performed on avideo PES packet formed with a TS packet of video data in order toobtain video data. The video data is subjected to graphic datasuperposing processing or the like by the graphic production circuit318, and then outputted to the video output terminal 319. In the MPEGdecoder 317, decoding processing is performed on an audio PES packetformed with a TS packet of audio data in order to obtain audio data. Theaudio data is outputted to the audio output terminal 320.

The video (image) data and audio data obtained by the MPEG decoder 317according to the partial TS reproduced by the DVD/BD drive 309 or HDD310 are fed to the HDMI transmitting unit 302, and transmitted to theaudio amplifier 200 over the HDMI cable 620 coupled to the HDMI terminal302.

In the high-speed data line interface 303, an encrypted partial TStransmitted from the audio amplifier 200 side over predetermined linesof the HDMI cable 620 coupled to the HDMI terminal 301 is received. Thepartial TS is fed to the DTCP circuit 316 via the Ethernet interface314, and decrypted thereby.

The partial TS decrypted by the DTCP circuit 316 is fed to the CPU 311.The CPU 311 analyzes the partial TS, and extracts a packet ID (PID)serving as channel selection information signifying what channel isselected in the television receiver 100. The CPU 311 controls thedigital tuner 305 and demultiplexer 306 on the basis of the packet ID,and permits selection of the same channel as the channel in thetelevision receiver 100. In this case, when the channel selected in thetelevision receiver 100 is changed to another, the channel selected inthe DVD recorder 300 is also changed to another.

In the high-speed data line interface 303, an IP packet containing aremote control code and being transmitted from the audio amplifier 200side over predetermined lines of the HDMI cable 620 coupled to the HDMIterminal 301 is received. The IP packet is fed to the CPU 311 via theEthernet interface 314. When the remote control code contained in the IPpacket relates to control of the DVD recorder 300, the CPU 311 controlsthe components of the DVD recorder 300 on the basis of the remotecontrol code.

For example, when the remote control code is what instructs recording,the CPU 311 implements control so that the partial TS extracted by thedemultiplexer 306 will be recorded by the DVD/BD drive 309 or HDD 310.

When the partial TS extracted by the demultiplexer 306 or the partial TSreproduced by the DVD/BD drive 309 or HDD 310 is transmitted over anetwork, after the partial TS is encrypted by the DTCP circuit 316, theresultant partial TS is outputted to the network terminal 315 via theEthernet interface 314.

FIG. 6 shows an example of the arrangement in the communication system10 shown in FIG. 1 of the HDMI receiving unit (HDMI sink) 102 of thetelevision receiver 100 and the HDMI transmitting unit (HDMI source) 202a of the audio amplifier 200.

The HDMI transmitting unit 202 a unidirectionally transmits differentialsignals of the baseband (non-compressed), which represent image data forone screen, to the HDMI receiving unit 102 on multiple channels duringan effective image interval (hereinafter, referred to as an active videointerval) that is an interval having a horizontal blanking period and avertical blanking period excluded from an interval from a certainvertical synchronizing signal to the next vertical synchronizing signal(hereinafter, referred to as a video field). During the horizontalblanking period and vertical blanking period, the HDMI transmitting unit202 a unidirectionally transmits differential signals, which representaudio data, a control packet, and other auxiliary data that accompanyimage data, to the HDMI receiving unit 102 on multiple channels.

The HDMI transmitting unit 202 a includes a source signal processingblock 71 and an HDMI transmitter 72. To the source signal processingblock 71, non-compressed image (video) data and audio data of thebaseband are fed. The source signal processing block 71 performsrequired processing on the fed image data and audio data, and feeds theresultant image data and audio data to the HDMI transmitter 72. Thesource signal processing block 71 transfers, if necessary, controlinformation or information indicating a status (control/status), to orfrom the HDMI transmitter 72.

The HDMI transmitter 72 converts the image data, which is fed from thesource signal processing block 71, into differential signals, andunidirectionally transmits the differential signals to the HDMIreceiving unit 102, which is connected over the HDMI cable 610, onmultiple channels, that is, three TMDS channels #0, #1, and #2.

The transmitter 72 converts audio data, a control packet, or any otherauxiliary data accompanying non-compressed image data, and control dataitems of a vertical synchronizing signal (VSYNC) and a horizontalsynchronizing signal (HSYNC), which are fed from the source signalprocessing block 71, into differential signals, and unidirectionallytransmits the differentials signals to the HDMI receiving unit 102,which is connected over the HDMI cable 610, on the three TMDS channels#0, #1, and #2.

The transmitter 72 transmits a pixel clock, which is synchronous withimage data items to be transmitted on the three TMDS channels #0, #1,and #2, to the HDMI receiving unit 102, which is connected over the HDMIcable 610, on a TMDS clock channel.

The HDMI receiving unit 102 receives differential signals, whichrepresent image data items and are unidirectionally transmitted from theHDMI transmitting unit 202 a on multiple channels, during an activevideo interval, and also receives differential signals, which representauxiliary data and control data items and are transmitted from the HDMItransmitting unit 202 a on multiple channels, during the horizontalblanking period and vertical blanking period.

The HDMI receiving unit 102 includes an HDMI receiver 81 and a sinksignal processing block 82. The HDMI receiver 81 receives thedifferential signals, which represent image data items and areunidirectionally transmitted from the HDMI transmitting unit 202 a,which is connected over the HDMI cable 610, on the TMDS channels #0, #1,and #2, and the differential signals, which represent the auxiliary dataand control data items, synchronously with the pixel clock transmittedon the TMDS clock channel from the HDMI transmitting unit 202 a.Further, the HDMI receiver 81 converts the differential signals into therepresentative image data items, auxiliary data, and control data items,and feeds, if necessary, the data items to the sink signal processingblock 82.

The sink signal processing block 82 performs required processing on thedata items fed from the HDMI receiver 81, and outputs the resultant dataitems. The sink signal processing block 82 transfers, if necessary,control information and information indicating a status (control/status)to or from the HDMI receiver 81.

The HDMI transmission channels include, in addition to the three TMDschannels #0, #1, and #2 on which image data items, auxiliary data, andcontrol data items are unidirectionally serially transmitted from theHDMI transmitting unit 202 a to the HDMI receiving unit 102synchronously with the pixel clock, and the TMDS clock channel servingas a transmission channel on which the pixel clock is transmitted,transmission channels called a display data channel (DDC) 83 and a CECline 84.

The DDC 83 is realized with two lines (signal lines) that are includedin the HDMI cable 610 and are not shown, and is used when sourceequipment reads enhanced-extended display identification (E-EDID) fromsink equipment connected over the HDMI cable 610. Namely, the sinkequipment includes an EDIDROM 85. The source equipment reads the E-EDID,which is stored in the EDIDROM 85, from the sink equipment, which isconnected over the HDMI cable 610, over the DDC 83, and recognizes thesettings and performance of the sink equipment on the basis of theE-EDID.

The CEC line 84 is formed with one line that is included in the HDMIcable 610 and is not shown, and is used to perform bidirectionalcommunication of control data items between source equipment and sinkequipment.

The HDMI cable 620 includes a line 86 coupled to a pin called Hot PlugDetect (HPD). Source equipment can detect connection of sink equipmentby utilizing the line 86. A line 87 to be used to supply power fromsource equipment to sink equipment is further included in the HDMI cable620. A reserved line 88 is further included in the HDMI cable 610.

FIG. 7 shows an example of transmission intervals (periods) during whichvarious kinds of transmission data items are transmitted on the threeTMDS channels #0, #1, and #2 conformable to the HDMI. FIG. 7 shows theintervals for the various kinds of transmission data items to betransmitted in a case where a progressive image of 720 pixelssideways×480 pixels lengthwise is transmitted on the TMDS channels #0,#1, and #2.

Within a video field during which transmitted data items are transmittedon the three TMDS channels #0, #1, and #2 conformable to the HDMI, threeintervals of a video data interval (video data period), a data islandinterval (data island period), and a control interval (control period)are defined.

The video field interval is an interval from the leading edge (activeedge) of a certain vertical synchronizing signal to the leading edge ofthe next vertical synchronizing signal, and is divided into a horizontalblanking period (horizontal blanking), a vertical blanking period(vertical blanking), and an active video interval (active video) that isan interval having the horizontal blanking period and vertical blankingperiod removed from the video field interval.

The video data interval is allocated to the active video interval.Within the video data interval, effective pixels (active pixel)corresponding to a product of 720 pixels×480 lines and constitutingnon-compressed image data items for one screen are transmitted duringthe video data interval.

The data island interval and control interval are allocated to thehorizontal blanking period and vertical blanking period. During the dataisland interval and control interval, auxiliary data is transmitted.

Specifically, the data island interval is allocated to parts of thehorizontal blanking period and vertical blanking periods. During thedata island interval, data out of the auxiliary data that does notrelate to control, for example, a packet of audio data is transmitted.

The control interval is allocated to the other parts of the horizontalblanking period and vertical blanking period. During the controlinterval, data out of the auxiliary data that does not relate tocontrol, for example, a vertical synchronizing signal, a horizontalsynchronizing signal, and a control packet are transmitted.

According to the ongoing HDMI, the frequency of a pixel clock to betransmitted on the TMDS clock channel is, for example, 165 MHz. In thiscase, the transfer rate for the data island interval is on the order ofapproximately 500 Mbps.

FIG. 8 shows the pin assignments of the HDMI terminals 101 and 201 arespectively. The pin assignments are called type A assignments.

Two lines that are differential lines over which differential signalsTMDS Data#i+ and TMDS Data#i− on the TMDS channel #i are transmitted arecoupled to a pin (any of pins whose pin numbers are 1, 4, and 7) towhich TMDS Data#i+ is assigned, and a pin (any of pins whose pin numbersare 3, 6, and 9) to which TMDS Data#i− is assigned.

The CEC line 84 over which a CEC signal representing control data istransmitted is coupled to a pin whose pin number is 13. A pin whose pinnumber is 14 is an unused (reserved) pin. A line over which a serialdata (SDA) signal such as E-EDID is transmitted is coupled to a pinwhose pin number is 16. A line over which a serial clock (SCL) signalthat is a clock signal to be used for synchronization at the time oftransmitting or receiving the SDA signal is transmitted is coupled to apin whose pin number is 15. The DDC 83 is formed with the line overwhich the SDA signal is transmitted and the line over which the SCLsignal is transmitted.

The line 86 which the source equipment 110 uses, as mentioned above, todetect connection of the sink equipment 120 is coupled to a pin whosepin number is 19. The line 87 to be used to, as mentioned above, supplypower is coupled to a pin whose pin number is 18.

FIG. 6 shows an example of the arrangement in the communication system10 shown in FIG. 1 of the HDMI transmitting unit (HDMI source) 202 a ofthe audio amplifier 200 and the HDMI receiving unit (HDMI sink) 102 ofthe television receiver 100. The HDMI transmitting unit 302 of the DVDrecorder 300 and the HDMI receiving unit 202 b of the audio amplifier200 in the communication system 10 shown in FIG. 1 are arranged in thesame manner, though a detail will be omitted.

FIG. 9 shows an example of the arrangement in the communication system10 shown in FIG. 1 of the high-speed data line interface 103 of thetelevision receiver 100 and the high-speed data line interface 203 a ofthe audio amplifier 200. The interfaces 103 and 203 a constitute acommunication unit that performs local-area network (LAN) communication.The communication unit performs communication using a pair ofdifferential lines out of the multiple lines constituting the HDMI cable610, that is, in the present embodiment, a reserved line (Ether-line)coupled to an unused (reserve) pin (14 pin) and an HPD line (Ether+line)coupled to an HPD pin (19 pin).

The audio amplifier 200 includes a LAN signal transmission circuit 411,a terminal resistor 412, ac-coupling capacitors 413 and 414, a LANsignal reception circuit 415, a subtraction circuit 416, a pull-upresistor 421, a resistor 422 and a capacitor 423 constituting a low-passfilter, a comparator 424, a pull-down resistor 431, a resistor 432 and acapacitor 433 constituting a low-pass filter, and a comparator 434.Herein, the high-speed data line interface 203 a is composed of the LANsignal transmission circuit 411, terminal resistor 412, ac-couplingcapacitors 413 and 414, LAN signal reception circuit 415, andsubtraction circuit 416.

Between a power line (+5.0 V) and a ground line, a series circuitcomposed of the pull-up resistor 421, ac-coupling capacitor 413,terminating resistor 412, ac-coupling capacitor 414, and pull-downresistor 431 is connected. A junction point P1 between the ac-couplingcapacitor 413 and terminating resistor 412 is connected to the positiveoutput side of the LAN signal transmission circuit 411, and alsoconnected to the positive input side of the LAN signal reception circuit415. A junction point P2 between the ac-coupling capacitor 414 andterminating resistor 412 is connected to the negative output side of theLAN signal transmission circuit 411, and also connected to the negativeinput side of the LAN signal reception circuit 415. To the input side ofthe LAN signal transmission circuit 411, a transmitted signal SG 411 isfed from the Ethernet interface 211.

To the positive terminal of the subtraction circuit 416, an outputsignal SG412 of the LAN signal reception circuit 415 is fed. To thenegative terminal of the subtraction circuit 416, the transmitted signalSG411 is fed from the Ethernet interface 211. In the subtraction circuit416, the transmitted signal SG411 is subtracted from the output signalSG412 of the LAN signal reception circuit 415. The output signal SG413of the subtraction circuit 416 is fed to the Ethernet interface 211.

A junction point Q1 between the pull-up resistor 421 and ac-couplingcapacitor 413 is connected to the ground line via the series circuitcomposed of the resistor 422 and capacitor 423. An output signal of thelow-pass filter developed at the junction point between the resistor 422and capacitor 423 is fed to one of the input terminals of the comparator424. In the comparator 424, the output signal of the low-pass filter iscompared with a reference voltage Vref1 (+3.75 V) fed to the other inputterminal. An output signal SG414 of the comparator 424 is fed to the CPU213 (not shown).

A junction point Q2 between the ac-coupling capacitor 414 and pull-downresistor 431 is connected to the ground line via the series circuit ofthe resistor 432 and capacitor 433. An output signal of the low-passfilter developed at the junction point between the resistor 432 andcapacitor 433 is fed to one of the input terminals of the comparator434. In the comparator 434, the output signal of the low-pass filter iscompared with a reference voltage Vref2 (+1.4 V) fed to the other inputterminal. An output signal SG415 of the comparator 434 is fed to the CPU213.

The television receiver 100 includes a LAN signal transmission circuit441, a terminating resistor 442, ac-coupling capacitors 443 and 444, aLAN signal reception circuit 445, a subtraction circuit 446, a pull-downresistor 451, a resistor 452 and a capacitor 453 constituting a low-passfilter, a comparator 454, a choke coil 461, a resistor 462, and aresistor 463. Herein, the high-speed data line interface 103 is composedof the LAN signal transmission circuit 441, terminating resistor 442,ac-coupling capacitors 443 and 444, LAN signal reception circuit 445,and subtraction circuit 446.

Between a power line (+5.0 V) and a ground line, a series circuit of theresistor 462 and resistor 463 is connected. Between a junction pointbetween the resistor 462 and resistor 463 and the ground line, a seriescircuit composed of the choke coil 461, ac-coupling capacitor 444,terminating resistor 442, ac-coupling capacitor 443, and pull-downresistor 451 is connected.

A junction point P3 between the ac-coupling capacitor 443 andterminating resistor 442 is connected to the positive output side of theLAN signal transmission circuit 441, and also connected to the positiveinput side of the LAN signal reception circuit 445. A junction point P4between the ac-coupling capacitor 444 and terminating resistor 442 isconnected to the negative output side of the LAN signal transmissioncircuit 441, and also connected to the negative input side of the LANsignal reception circuit 445. To the input side of the LAN signaltransmission circuit 441, a transmitted signal SG 417 is fed from theEthernet interface 124.

To the positive terminal of the subtraction circuit 446, an outputsignal SG418 of the LAN signal reception circuit 445 is fed. To thenegative terminal of the subtraction circuit 446, the transmitted signalSG417 is fed from the Ethernet interface 124. In the subtraction circuit446, the transmitted signal SG417 is subtracted from the output signalSG418 of the LAN signal reception circuit 445. The output signal SG419of the subtraction circuit 446 is fed to the Ethernet interface 124.

A junction point Q3 between the pull-down resistor 451 and ac-couplingcapacitor 443 is connected to the ground line via a series circuit ofthe resistor 452 and capacitor 453. An output signal of the low-passfilter developed at the junction point between the resistor 452 andcapacitor 453 is fed to one of the input terminals of the comparator454. In the comparator 454, the output signal of the low-pass filter iscompared with a reference voltage Vref3 (+1.25 V) fed to the other inputterminal. An output signal SG416 of the comparator 454 is fed to the CPU121 (not shown).

The reserved line 501 and HPD line 502 included in the HDMI cable 610constitute a differential twisted pair. The source-side end 511 of thereserved line 501 is coupled to the 14 pin of the HDMI terminal 201 a,and the sink-side end of the reserved line 501 is coupled to the pin 521(14 pin) of the HDMI terminal 101. The source-side end 512 of the HPDline 502 is coupled to the 19 pin of the HDMI terminal 201 a, and thesink-side end 522 of the HPD line 502 is coupled to the 19 pin of theHDMI terminal 101.

In the audio amplifier 200, the junction point Q1 between the pull-upresistor 421 and ac-coupling capacitor 413 is connected to the 14 pin ofthe HDMI terminal 201 a. The junction point Q2 between the pull-downresistor 431 and ac-coupling capacitor 414 is connected to the 19 pin ofthe HDMI terminal 201 a. On the other hand, in the television receiver100, the junction point Q3 between the pull-down resistor 451 andac-coupling capacitor 443 is connected to the 14 pin of the HDMIterminal 101. The junction point Q4 between the choke coil 461 andac-coupling capacitor 444 is connected to the 19 pin of the HDMIterminal 101.

Next, the actions for LAN communication performed by the high-speed dataline interfaces 103 and 203 a having the foregoing components will bedescribed below.

In the audio amplifier 200, the transmitted signal SG411 outputted fromthe Ethernet interface 211 is fed to the input side of the LAN signaltransmission circuit 411. Differential signals (a positive output signaland a negative output signal) associated with the transmitted signalSG411 are outputted from the LAN signal transmission circuit 411. Thedifferential signals outputted from the LAN signal transmission circuit411 are fed to the junction points P1 and P2 respectively, andtransmitted to the television receiver 100 over a pair of lines (thereserved line 501 and HPD line 502) included in the HDMI cable 610.

In the television receiver 100, the transmitted signal SG417 outputtedfrom the Ethernet interface 124 is fed to the input side of the LANsignal transmission circuit 441, and differential signals (a positiveoutput signal and a negative output signal) associated with thetransmitted signal SG417 are outputted from the LAN signal transmissioncircuit 441. The differential signals outputted from the LAN signaltransmission circuit 441 are fed to the junction points P3 and P4respectively, and transmitted to the audio amplifier 200 over a pair oflines (the reserved line 501 and HPD line 502) of the HDMI cable 610.

In the audio amplifier 200, since the input side of the LAN signalreception circuit 415 is connected to the junction points P1 and P2, anadditive signal between the transmitted signal associated with thedifferential signals (current signals) outputted from the LAN signaltransmission circuit 441 and the received signal associated with thedifferential signals transmitted from the television receiver 100 asmentioned above is obtained as the output signal SG412 of the LAN signalreception circuit 415. In the subtraction circuit 416, the transmittedsignal SG411 is subtracted from the output signal SG412 of the LANsignal reception circuit 415. Therefore, the output signal SG413 of thesubtraction circuit 416 corresponds to the transmitted signal SG417 ofthe television receiver 100.

In the television receiver 100, since the input side of the LAN signalreception circuit 445 is connected to the junction points P3 and P4, anadditive signal between the transmitted signal associated with thedifferential signals (current signals) outputted from the LAN signaltransmission circuit 441 and the received signal associated with thedifferential signals transmitted from the audio amplifier 200 asmentioned above is obtained as the output signal SG418 of the LAN signalreception circuit 445. In the subtraction circuit 446, the transmittedsignal SG417 is subtracted from the output signal SG418 of the LANsignal reception circuit 445. Therefore, the output signal SG419 of thesubtraction circuit 446 corresponds to the transmitted signal SG411 ofthe audio amplifier 200.

Between the high-speed data line interface 103 of the televisionreceiver 100 and the high-speed data line interface 203 a of the audioamplifier 200, bidirectional LAN communication can be performed.

In FIG. 9, the HPD line 502 is used for, in addition to the LANcommunication, propagation to the audio amplifier 200 of the fact thatthe HDMI cable 610 has been plugged into the television receiver 100 ata DC bias level. Specifically, when the HDMI cable 610 is plugged intothe television receiver 100, the resistors 462 and 463 and the chokecoil 461 in the television receiver 100 bias the HPD line 502 toapproximately 4 V through the 19 pin of the HDMI terminal 101. The audioamplifier 200 uses the lo-pass filter, which is composed of the resistor432 and capacitor 433, to sample the dc bias on the HPD line 502, anduses the comparator 434 to compare the dc bias with a reference voltageVref2 (for example, 1.4 V).

When the HDMI cable 610 is not plugged into the television receiver 100,the voltage at the 19 pin of the HDMI terminal 201 a is lower than thereference voltage Vref2 because of presence of the pull-down resistor431. In contrast, when the HDMI cable 610 is plugged into the televisionreceiver 100, the voltage at the 19 pin is higher than the referencevoltage Vref2. Therefore, when the HDMI cable 610 is plugged into thetelevision receiver 100, the output signal SG415 of the comparator 434assumes a high level. Otherwise, the output signal SG415 assumes a lowlevel. Therefore, based on the output signal SG415 of the comparator434, the CPU 213 of the audio amplifier 200 can recognize whether theHDMI cable 610 has been plugged into the television receiver 100.

In FIG. 9, the pieces of equipment interconnected at both the ends ofthe HDMI cable 610 have the function of recognizing based on the dc biaspotential on the reserved line 501 whether the remote equipment isequipment supporting LAN communication (hereinafter, referred to ase-HDMI compatible equipment) or equipment not supporting LANcommunication (hereinafter, referred to as e-HDMI incompatibleequipment).

As mentioned above, the audio amplifier 200 pulls up (+5 V) the reservedline 501 using the resistor 421, and the television receiver 100 pullsdown the reserved line 501 using the resistor 451. The resistors 421 and451 do not exist in the e-HDMI incompatible equipment.

The audio amplifier 200 uses, as mentioned above, the comparator 424 tocompare the dc potential on the reserved line 501, which has passedthrough the low-pass filter composed of the resistor 422 and capacitor423, with the reference voltage Vref1. When the television receiver 100is e-HDMI compatible equipment and includes the pull-down resistor 451,the voltage on the reserved line 501 is 2.5 V. However, when thetelevision receiver 100 is e-HDMI incompatible equipment and does notinclude the pull-down resistor 451, the voltage on the reserved line 501is 5 V because of presence of the pull-up resistor 421.

Therefore, when the reference voltage Vref1 is set to, for example, 3.75V, if the television receiver 100 is e-HDMI compatible equipment, theoutput signal SG414 of the comparator 424 assumes a low level.Otherwise, the output signal SG414 assumes a high level. The CPU 213 ofthe audio amplifier 200 can recognize based on the output signal SG414of the comparator 424 whether the television receiver 100 is e-HDMIcompatible equipment.

Likewise, the television receiver 100 uses, as mentioned above, thecomparator 454 to compare the dc potential on the reserved line 501,which has passed through the low-pass filter composed of the resistor452 and capacitor 453, with the reference voltage Vref3. When the audioamplifier 200 is e-HDMI compatible equipment and includes the pull-upresistor 421, the voltage on the reserved line 501 is 2.5 V. However,when the audio amplifier 200 is e-HDMI incompatible equipment and doesnot include the pull-up resistor 421, the voltage on the reserved line501 is 0 V because of presence of the pull-down resistor 451.

When the reference voltage Vref3 is set to, for example, 1.25 V, if thesource equipment 110 is e-HDMI compatible equipment, the output signalSG416 of the comparator 454 assumes the high level. Otherwise, theoutput signal SG416 of the comparator 454 assumes the low level. Basedon the output signal SG416 of the comparator 454, the CPU 121 of thetelevision receiver 100 can recognize whether the audio amplifier 200 ise-HDMI compatible equipment.

The pull-up resistor 421 shown in FIG. 9 may be included in the HDMIcable 610 other than the audio amplifier 200. In this case, theterminals of the pull-up resistor 421 are connected onto lines (signallines), which are spliced or coupled to the reserved line 501 or a powersupply (supply potential) respectively, out of the lines included in theHDMI cable 610.

The pull-down resistor 451 and resistor 463 shown in FIG. 9 may beincluded in the HDMI cable 610 other than the television receiver 100.In this case, the terminals of the pull-down resistor 451 are connectedonto the reserved line 501 and a line (ground line), which is coupled tothe ground (reference potential), out of the lines included in the HDMIcable 610. The terminals of the resistor 463 are connected onto the HPDline 502 and the line (ground line), which is coupled to the ground(reference potential), out of the lines included in the HDMI cable 610.

FIG. 9 shows an example of the arrangement in the communication system10 shown in FIG. 1 of the high-speed data line interface 103 of thetelevision receiver 100 and the high-speed data line interface 203 a ofthe audio amplifier 200. The high-speed data line interface 203 b of theaudio amplifier 200 and the high-speed data line interface 303 of theDVD recorder 300 included in the communication system 10 shown in FIG. 1are arranged in the same manner.

Next, various operating sequences in the communication system 10 shownin FIG. 1 will be described below. To begin with, referring to thesequence diagram of FIG. 10, a “one-touch recording” sequence forrecording a picture (image) being seen on the television receiver 100will be described below.

(a) When a user uses the remote control transmitter 127 to perform areceiving channel changing manipulation (channel change), (b) the CPU121 of the television receiver 100 controls the digital tuner 106 anddemultiplexer 107 so as to attain a receiving state for the channelselected by the user.

(c) When a receiving channel is changed to another as mentioned above,the television receiver 100 uses the DTCP circuit 116 to encrypt apartial TS extracted by the demultiplexer 107, and then transmits theresultant TS to the DVD recorder 300 via the Ethernet interface 124 andhigh-speed data line interface 103.

(d) The DVD recorder 300 uses the high-speed data line interface 303 toreceive the partial TS sent from the television receiver 100, and usesthe DTCP circuit 306 to decrypt the partial TS. The CPU 311 of the DVDrecorder 300 controls the digital tuner 305 and demultiplexer 306 on thebasis of channel selection information (packet ID) contained in thepartial TS so as to attain a receiving state for the same channel as thechannel received by the television receiver 100.

(e) Thereafter, when the user uses the remote control transmitter 127 toinstruct recording (one-touch record), the CPU 121 of the televisionreceiver 100 (f) produces an IP packet which contains a remote controlcode (remote control signal) instructing recording and being received bythe remote control receiving unit 126, and (g) transmits the IP packetto the DVD recorder 300 via the Ethernet interface 124 and high-speeddata line interface 103.

(h) The DVD recorder 300 receives the IP packet sent from the televisionreceiver 100 using the high-speed data line interface 303. The CPU 311of the DVD recorder 300 allows the DVD/BD drive 309 or HDD 310 toinitiate recording of the partial TS, which is extracted by thedemultiplexer 306, on the basis of the remote control code instructingrecording and being contained in the IP packet.

(i) The CPU 311 of the DVD recorder 300 produces an IP packet that hasrecording status information concerning the DVD/BD drive 309 or HDD 310contained in a payload thereof, and transmits the IP packet to thetelevision receiver 100 via the Ethernet interface 314 and high-speeddata line interface 303.

(j) The television receiver 100 receives the IP packet sent from the DVDrecorder 300 using the high-speed data line interface 103. The CPU 121controls, if necessary, the graphic production circuit 110 on the basisof the recording status information contained in the IP packet, anddisplays the recording status on the display panel 112 while superposingthe recording status on an image.

According to the “one-touch recording” sequence mentioned in FIG. 10,when the receiving channel of the television receiver 100 is changed toanother, a partial TS containing channel selection information isimmediately transmitted to the DVD recorder 300 side via the high-speeddata line interface 103. The receiving channel of the DVD recorder 300is then changed to another. When a user instructs recording, an IPpacket containing a remote control command that instructs recording isimmediately transmitted to the DVD recorder 300 via the high-speed dataline interface 103. Therefore, recording of the partial TS on thereceiving channel on which the television receiver 100 is viewed can beimmediately initiated in the DVD recorder 300.

Incidentally, FIG. 11 shows as a comparative example the “one-touchrecording” sequence to be followed in a case where the pieces ofequipment of the communication system 10 shown in FIG. 1 do not includethe high-speed data line interface.

(a) When a user uses the remote control transmitter 127 to perform areceiving channel changing manipulation (channel change), (b) the CPU121 of the television receiver 100 controls the digital tuner 106 anddemultiplexer 107 so as to attain a receiving state for a channelselected by the user.

(c) Thereafter, when the user uses the remote control transmitter 127 toinstruct recording (one touch record), the CPU 121 of the televisionreceiver 100 (d) converts a remote control code, which instructsrecording and is received by the remote control receiving unit 126, intoa command employed in HDMI CEC control, and (e) transmits the command tothe DVD recorder 300 using the CEC line.

(f) After receiving the recording instructing command, the DVD recorder300 inquires the television receiver 100 for receiving channelinformation using the CEC line. (g) In response to the inquiry, thetelevision receiver 100 transmits the receiving channel information tothe DVD recorder 300 using the CEC line.

(h) Based on the receiving channel information sent from the televisionreceiver 100, the CPU 311 of the DVD recorder 300 controls the digitaltuner 305 and demultiplexer 306 so as to square the receiving channelthereof with the receiving channel of the television receiver 100, and(i) allows the DVD/BD drive 309 or HDD 310 to initiate recording of thepartial TS extracted by the demultiplexer 306.

(j) The CPU 311 of the DVD recorder 300 transmits the recording statusinformation on the DVD/BD drive 309 or HDD 310 to the televisionreceiver 100 using the CEC line. (k) Based on the recording statusinformation sent from the DVD recorder 300, the television receiver 100controls, if necessary, the graphic production circuit 110, and displaysthe recording status on the display panel 112 while superposing therecording status on an image.

According to the “one-touch recording” sequence mentioned in FIG. 11,after a user instructs recording, the receiving channel of the DVDrecorder 300 is squared with the receiving channel of the televisionreceiver 100 in order to initiate recording. Transmission of a recordinginstructing command from the television receiver 100 to the DVD recorder300, inquiry for receiving channel information from the DVD recorder 300to the television receiver 100, and transmission of the receivingchannel information from the television receiver 100 to the DVD recorder300 are performed using the CEC line characteristic of a lowtransmission speed. Therefore, a very long time is required untilrecording is initiated after a user instructs recording.

Next, referring to the sequence diagram of FIG. 12, a “theater mode”sequence for changing audio outputs between the television receiver 100and audio amplifier 200 will be described below.

(a) When a user uses the remote control transmitter 127 to designate a“theater mode,” (b) the CPU 121 of the television receiver 100 controlsthe audio amplification circuit 114 so as to mute the audio output ofthe loudspeaker 115. (c) The CPU 121 of the television receiver 100 thenproduces an IP packet containing a muting canceling command for theaudio amplifier 200, and transmits the IP packet to the audio amplifier200 via the Ethernet interface 124 and high-speed data line interface103.

(d) The audio amplifier 200 receives the IP packet sent from thetelevision receiver 100 using the high-speed data line interface 203 a.Based on the muting canceling command contained in the IP packet, theCPU 213 controls the audio amplification circuit 208 so as to cancelmuting of the audio output of the 5.1-channel loudspeaker group 500.Accordingly, a state in which sounds are outputted through theloudspeaker 115 of the television receiver 100 is switched to the“theater mode” in which sounds are outputted through the loudspeakergroup 500 connected to the audio amplifier 200.

In this case, the television receiver 100 uses the DTCP circuit 116 toencrypt the partial TS extracted by the demultiplexer 107, and thentransmits the resultant partial TS to the audio amplifier 200 via theEthernet interface 124 and high-speed data line interface 103. The audioamplifier 200 receives the partial TS sent from the television receiver100 using the high-speed data line interface 203 a, and outputs an audiosignal, which represents audio data contained in the partial TS, fromthe audio processing circuit 207. Therefore, when the audioamplification circuit 208 is controlled as mentioned above in order tocancel muting of the audio output of the 5.1-channel loudspeaker group500, sounds are immediately outputted through the loudspeaker group 500.

(e) After canceling muting, the CPU 213 of the audio amplifier 200produces an IP packet having the result contained in a payload thereof,and transmits the IP packet to the television receiver 100 via theEthernet interface 211 and high-speed data line interface 203 a.

According to the “theater mode” sequence mentioned in FIG. 12, when auser designates the “theater mode,” the audio output of the loudspeaker115 of the television receiver 100 is muted, and an IP packet containinga muting canceling command is immediately transmitted to the audioamplifier 200 via the high-speed data line interface 103. Therefore, thestate in which sounds are outputted through the loudspeaker 115 of thetelevision receiver 100 can be immediately switched to the “theatermode” in which sounds are outputted through the loudspeaker group 500connected to the audio amplifier 200.

FIG. 13 shows as a comparative example the “theater mode” sequence to beemployed in a case where the pieces of equipment of the communicationsystem 10 shown in FIG. 1 do not include the high-speed data lineinterface.

(a) When a user uses the remote control transmitter 127 to designate the“theater mode,” (b) the CPU 121 of the television receiver 100 controlsthe audio amplification circuit 114 so as to mute the audio output ofthe loudspeaker 115. (c) The television receiver 100 inquires the audioamplifier 200 for a muting situation using the CEC line. (d) In responseto the inquiry for the muting situation, the audio amplifier 200transmits the muting situation to the television receiver 100 using theCEC line.

(e) When muting is not canceled in the audio amplifier 200, the CPU 121of the television receiver 100 returns a CEC command, which instructsmuting cancelation, to the audio amplifier 200 using the CEC line. (f)Based on the CEC command, the audio amplifier 200 controls the audioamplification circuit 208 so as to cancel muting of the audio output ofthe 5.1-channel loudspeaker group 500. Accordingly, the state in whichsounds are outputted through the loudspeaker 115 of the televisionreceiver 100 is switched to the “theater mode” in which sounds areoutputted through the loudspeaker group 500 connected to the audioamplifier 200. If the high-speed data line interface is not included,feeding audio data from the television receiver 100 to the audioamplifier 200 is achieved over, for example, an optical cable.

(g) After canceling muting, the CPU 213 of the audio amplifier 200transmits the result to the television receiver 100 using the CEC line.

According to the “theater mode” sequence mentioned in FIG. 13, after auser designates the “theater mode,” the television receiver 100 inquiresthe audio amplifier 200 for a muting situation. If muting is notcanceled, the television receiver 100 transmits a CEC command, whichinstructs muting cancelation, to the audio amplifier 200 so as to switchthe state to the “theater mode.” Therefore, the time that elapses untilthe state is actually switched to the “theater mode” after the userdesignates the “theater mode” gets longer. According to the “theatermode” control sequence mentioned in FIG. 13, the optical cable overwhich audio data is transmitted is needed in addition to the HDMI cable610.

Referring to the sequence diagram of FIG. 14, a “remote control”sequence will be described below. Incidentally, FIG. 14 is concernedwith a case where a remote control code is transmitted from thetelevision receiver 100 to the DVD recorder 300.

(a) While a user is depressing a predetermined button (remote controlbutton) of the remote control transmitter 127, the CPU 121 of thetelevision receiver 100 (b) produces an IP packet containing a remotecontrol code received by the remote control receiving unit 126, and (c)transmits the IP packet to the DVD recorder 300 via the Ethernetinterface 124 and high-speed data line interface 103.

(d) The DVD recorder 300 receives the IP packet sent from the televisionreceiver 100 using the high-speed data line interface 303. The CPU 311of the DVD recorder 300 interprets the remote control code contained inthe IP packet and controls the relevant part of the DVD recorder 300. Inthis case, the CPU 311 can learn the length of the user's depression ofthe button from the receiving duration for the IP packet, and caninterpret the remote control code in consideration of the length of thedepression.

(e) When the user ceases depression of the predetermined button of theremote control transmitter 127, (f) the CPU 121 of the televisionreceiver 100 terminates production of the IP packet containing theremote control code.

According to the “remote control” sequence mentioned in FIG. 14, thetelevision receiver 100 produces an IP packet containing a remotecontrol code, transmits the IP packet to the DVD recorder 300 via thehigh-speed data line interface 103, and controls the actions in the DVDrecorder 300. Therefore, in the television receiver 100, the processingof converting the remote control code into, for example, a code definedunder the CEC becomes unnecessary. Likewise, in the DVD recorder 300,the processing of converting the code defined under the CEC into theoriginal remote control code becomes unnecessary. The pieces ofprocessing on the transmitting and receiving sides respectively of theremote control code are simplified. The television receiver 100transmits an IP packet containing the remote control code to the DVDrecorder 300 via the high-speed data line interface 103. Remote controlof the DVD recorder 300 from the television receiver 100 side can bequickly achieved.

FIG. 15 shows as a comparative example a “remote control” sequence to beemployed in a case where the pieces of equipment of the communicationsystem 10 shown in FIG. 1 do not include the high-speed data lineinterface.

(a) When a user depresses a predetermined button of the remote controltransmitter 127, (b) the CPU 121 of the television receiver 100 convertsa remote control code received by the remote control receiver 126 into aCEC command according to a code list defined under the CEC. (c) The CPU121 transmits the CEC command to the DVD recorder 300 using the CECline. (d) The CPU 311 of the DVD recorder 300 reconverts the CEC commandsent from the television receiver 100 into the remote control code,interprets the remote control code, and controls the relevant part ofthe DVD recorder 300.

(e) Thereafter, if the user ceases depression of the predeterminedbutton of the remote control transmitter 127, the CPU 121 of thetelevision receiver 100 (f) produces a command defined under the CEC,and (g) transmits the CEC command to the DVD recorder 300 using the CECline. (h) The CPU 311 of the DVD recorder 300 terminates interpretationof the remote control code on the basis of a command signifying cease ofthe depression of the remote control button and being sent from thetelevision receiver 100.

According to the “remote control” sequence mentioned in FIG. 15, thetelevision receiver 100 converts a remote control code into a CECcommand according to the code list defined under the CEC, and transmitsthe CEC command to the DVD recorder 300. The DVD recorder 300 reconvertsthe sent CEC command into the remote control code and interprets theremote control code. The processing loads incurred by the transmittingand receiving sides of the remote control code are therefore increased.Since the CEC line characteristic of a low transmission speed is used tosend the remote control code, if the data length of the CEC command islong, a delay may be invited to the remote control of the DVD recorder300 from the television receiver 100 side.

As described so far, in the communication system 10 shown in FIG. 1, thebidirectional communication unit using two lines (the reserved line andHPD line) of the HDMI cable 610 or 620 is used to transmit channelselection information, a remote control code instructing recording,“theater mode” designating information, a remote control code, or thelike from the television receiver 100 to the audio amplifier 200 or DVDrecorder 300. The operating state of the audio amplifier 200 or DVDrecorder 300 can be quickly controlled.

In the foregoing embodiment, the high-speed bidirectional communicationunit using the reserved line and HPD line of the HDMI cable has beendescribed. The high-speed bidirectional communication unit may beconstructed using the other lines of the HDMI cable.

In the aforesaid embodiment, a description has been made on theassumption that the interface conformable to the HDMI standards isadopted as a transmission line between pieces of equipment. Theinvention can apply to any other similar transmission standards. In theaforesaid embodiment, the communication system 10 includes thetelevision receiver 100, audio amplifier 200, and DVD recorder 300. Theinvention can apply to a similar communication system including theother pieces of equipment.

In the aforesaid embodiment, bidirectional IP communication is performedbetween pieces of equipment. Bidirectional communication can beperformed under any protocol other than the IP. In the aforesaidembodiment, the pieces of equipment are interconnected over the HDMIcable.

The invention can also apply to a case where the pieces of equipment areinterconnected by radio.

INDUSTRIAL APPLICABILITY

The invention permits quick control of the operating state of sourceequipment side from sink equipment, and can apply to a communicationsystem having multiple pieces of equipment HDMI-interconnected.

What is claimed is:
 1. A communication method for performingtransmission of video data and audio data, communication of devicecontrol data, and local area network communication by using a singlecable, the method comprising the steps of: connecting a connectabledevice to a pair of differential transmission lines; performing thelocal area network communication through bidirectional communication viathe pair of differential transmission lines; and notifying a connectionstate of an interface with the connectable device by using a DC biaspotential of at least one of the differential transmission lines of thepair; wherein the connection state includes a first notification from afirst one of the pair of differential transmission lines whether theconnectable device is connected to the single cable.